The heart, like other muscles, is caused to contract by electrical stimulation by nerve fibres. The normal electrical conduction system allows the nerve impluse that is generated by the sinoatrial node of the heart to be propagated to and stimulate the myocardium to contract in an orderly progression, resulting in an efficient heart beat. When the nerve impulses proceed in the normal functional manner, the heart is said to be eurhthymic. When the nerve impulses are reduced or non-uniform the heart is said to be arrhythmic. Arrhythmias may be paroxysmal, that is, acute and short lasting, or chronic.
Extrasystole, or skipped beat, is generally an acute, recurrent event which can be caused by underlying heart disease, valve defects, or may be induced by triggers such as caffeine, nicotine or alcohol. Extrasystole can be felt as “palpitations” and although disturbing, is not, in itself dangerous. Therapy comprises treatment of an underlying heart condition and avoidance of triggers.
Tachycardia is an increased heart rate and can be caused by any trigger that raises the adrenaline levels, such as stress, exercise, strong emotion, caffeine or amphetamine. Heart rate returns to normal as the condition subsides. A severe form of arrhythmia is paroxysmal tachycardia, in which the ventricles contract rapidly and for a prolonged time in the absence of triggers or after the trigger has subsided. The condition is difficult to treat and can be fatal, as the ventricles may pass into fibrillation, in which the blood pressure drops to zero and circulation is halted. Immediate intervention with a defibrillating machine is necessary to preserve life.
Atrial fibrillation is a less serious occurrence. When the atria quiver in fibrillation, blood is not passed to the ventricles efficiently. Circulation is not generally impaired if the period of fibrillation is short; however, the stagnated pool of blood may clot and the clots may be passed to the pulmonary circulatory bed, the coronary arteries, the brain or other organs. It is estimated that about 2.2 million Americans suffer from atrial fibrillation and about 15% of strokes are related to this condition. Paroxysmal atrial fibrillation may have vague symptoms of unease during an attack or the subject may be completely unaware of the condition. Diagnosis is made by the absence of the P wave, representing depolarization of the atria, on EKG.
Atrial fibrillation may be treated with medications which slow the heart rate, “thinning” the blood with aspirin or warfarin to protect the patient from clotting, controlling the heart rate with beta blockers, calcium channel blockers or cardiac glycoside. Electrocardioversion may give persistent normalizing results.
The need remains for a simple treatment with no side effects to help control arrhythmias.